In a photolithography process, a wafer illumination unit can be used for illuminating a photoresist applied to the wafer. The illumination takes place through a mask, in such a way that in accordance with the shadow of the mask particular regions of the photoresist are not illuminated. As a function of the illumination, physical properties of the photoresist change in such a way that it can be removed in part in a subsequent step, resulting in a (positive or negative) photoresist image of the mask being left on the surface of the wafer.
In subsequent steps, the wafer can subsequently be processed to produce three-dimensional structures. In this way, for example semiconductor chips or MEMSs (microelectromechanical systems) can be produced.
For correct illumination of the photoresist, it is important that the mask is positioned at a precisely defined distance from the wafer. For this purpose, a plurality of the spacers may be used which are displaced from the inactive to the active position by the spacer displacement device when they are required so as to position the mask.
FIGS. 1 and 2 show a known wafer illumination unit 10 along with the spacer displacement devices used therein. A total of three spacer displacement devices 12, 14, 16 are attached to a base body 11 of the wafer illumination unit. These each contain an actuator 18 to which a pivot arm 20 is assigned. In each case a spacer, for example a spacer ball (“proximity ball”) or a disc, a roller etc., is attached to the free end of the pivot arm 20, remote from the pivot axis.
To displace the pivot arms 20 from the inactive position shown in FIG. 1 to the active position shown in FIG. 2, each actuator 18 comprises a toothed rod which acts on a gearwheel segment 22 which is attached to each pivot arm 20 concentric with the pivot axis thereof. When the toothed rod is displaced in translation inside the actuator 18, this leads to a pivot movement of the pivot arm 20.
The known construction is relatively complex.
The object of the invention is therefore to provide a spacer displacement device which is of a simpler construction and operates more reliably.